, although this term tends to be negative or pejorative towards tannins.
Tannins in grapes
The tannin content in wine depends mainly on the vinification (fermentation and ageing) as well as on the grape varieties. Varieties rich in tannins include Aglianico, Alicante Henri Bouschet, Blaufränkisch, Cabernet Sauvignon, Cot (Malbec), Mandilaria, Monastrell (Mourvèdre), Nebbiolo, Petit Verdot, Sangiovese, Syrah and Tannat. Low-tannin varieties or those with "soft tannins" are Carmenère, Cinsaut, Gamay, Garnacha Tinta, Merlot, Pinot Noir, St. Laurent, Schiava (Vernatsch, Trollinger) and Zweigelt. The longer the duration of maceration in red wines or the more strongly the mash is pressed, the more tannins and anthocyanins (colouring agents) are extracted.
into the wine.
The main part in the wine comes from the seeds, crests (caps, stems) and the skins of
grapes; only a very small part also comes from the pulp. That is why they are also called "grape-borne tannins". The smaller proportion comes from the wood during
barrel ageing or
barrique ageing.. These are therefore called "woody tannins". In the meantime, there are so-called oenological tannins for both groups that can be added (see below).
Tannins in wine
All tannins are odourless, easily oxidised and soluble in water, ethanol and acetone. They react with proteins. Therefore, protein turbidity in red wines is rather rare, since the insoluble tannin-protein compounds precipitate and are already removed with the lees. Tannins are an essential characteristic component of red wines in particular and to a lesser extent also of white wines. They are responsible for the characteristic bitter-tart and astringent effect, which, by the way, is not a taste sensation but a trigeminal.
sensation.
Around 30 different plant tannins are known in viticulture (but there are many more types). Some are important for the
quality of wine, others are considered unfavourable. The content of tannins and their structure are a decisive factor for the
quality of a wine. A late harvest and high
physiological ripeness ensure riper tannins that are perceived as
soft. Immature tannins, on the other hand, taste
green,
aggressive and
furry. Tannins prevent the
oxidation of the wine, but this can also be achieved by adding
potassium pyrosulphite. The tannin content of a wine does not so much determine its
storability as its need for storage. This means that wines with a high tannin content need a longer time (several years to decades) to reach their peak or optimal
drinking maturity..
During
barrel ageing, small amounts of
oxygen are added through the wood pores, which promotes the
polymerisation of the tannins with the
anthocyanins (pigments). This is why the tannin content of a wine after
barrel ageing is usually lower than before. In the course of
bottle ageing, further polymerisation takes place with non-astringent, long-chain molecules that sink to the
bottom of the bottle as a
deposit. This results in a
milder.taste.
Tannins vary greatly in their chemical structure and biological activity. Based on their chemical properties, they are divided into two groups. The
hydrolysable tannins are divided into ellagtannins and gallotannins, which in turn consist of a variety of species such as corilagin, grandinin, geraniin, isoterchebin, roburin and vescalagin. Through
hydrolysis and
oxidation, they can be converted into
glucose, other polyhydric
alcohols,
ellagic acid and
gallic acid. The second group are the
condensed tannins or
flavonoid tannins. These include the
catechins.
Tannin index
In white wines the tannin content is 0.3 g/l, but in red wines up to 2.5 g/l (see a list of all wine constituents under total extract). The tannin index was developed for objective measurability. The low proportion in white wines is mainly due to the type of vinification, as no combs and grape seeds are usually involved in fermentation here. Only at skin contact is a higher tannin content also achieved in white wines.
Oenological tannins
Since the mid-1980s, various techniques have been used in red winemaking to improve the taste in the direction of "mild" on the one hand and to improve the positive effect of the tannins on texture and shelf life during ageing or bottle ageing on the other. In the case of barrique ageing in particular, these are the proportion of new barrels, the type of oak and the extent of toasting, regulation of the tannin content by fining, and a targeted, dosed supply of oxygen by means of micro-oxygenation. What is new is the use of oenological tannins (mainly wood-based), which are used individually during winemaking: during maceration, after BSA, before barrel ageing or before bottling. In any case, the not uncontroversial use has a taste-altering effect. Two negative terms for tannin taste are green tannins and tannin to lose. See also under wine talk and wine rating.
oenological tannin: By Simon A. Eugster - Own work, CC BY 3.0, Link
Barrique barrel: By Gerard Prins - Own work, CC BY-SA 3.0, Link
Grape varieties: Ursula Brühl, Doris Schneider, Julius Kühn-Institut (JKI)
